Question

An element X has three shells. The valence shell has one electron more than twice the number of electrons as there are in its first shell:

A) Write its electronic configuration and valency.

B) Predict the nature of element X with reason.

  C)  Derive the formula of the compound formed when X reacts with sodium

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Answer 1

The element X is chlorine.

• The atomic number of chlorine is 17, therefore its electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁵ and its valency is 1 because it is the number of atoms that an element needs to complete its shell.
• Chlorine is highly reactive in nature due to its electronic configuration as it needs only one atom to attain the noble gas configuration.
• Na + Cl → NaCl, when X (Cl) reacts with sodium it forms common salt.